James Cameron, the director of the 2009 sci-fi blockbuster, has revealed that Sam Worthington had competition from the two huge stars for the lead part, but the relatively unknown actor won over the 64-year-old filmmaker with the ''intensity'' of his voice on the final speech in the movie.

''I really liked Channing's appeal. I liked Chris' appeal. They were both great guys.

''But Sam had a quality of voice and a quality of intensity.

''Everybody did about the same on all the material through the script, except for the final speech where he stands up and says, 'This is our land, ride now, go as fast as the wind can carry you.'

''That whole thing.

''I would have followed him into battle.

''And I wouldn't have followed the other guys.

''They've since gone onto fantastic careers and all that, but Sam was ready. He was ready.''

Meanwhile, Edie Falco recently joined the 'Avatar' franchise.

The 55-year-old actress is set to star in Cameron's four upcoming sequels as General Ardmore.

Although plot details are being kept under wraps, The 'Sopranos' star's character has been described as the leader of the fictional Resources Development Administration, the largest single non-governmental organisation in human space.

The official 'Avatar' Twitter account announced: ''We are thrilled to share that Edie Falco is joining the #AvatarFamily as General Ardmore, the Commander in charge of the RDA's interests in the Avatar Sequels! (sic)''

The original film is set on the alien world of Pandora inhabited by the Na'vi, beings who appear primitive but are highly evolved, as the planet's environment is poisonous, human/Na'vi hybrids, called Avatars, must link to human minds to allow for free movement on the planet.

Sully (Worthington), a paralysed former marine becomes mobile again through one such Avatar and falls in love with a Na'vi woman (Zoe Saldana), however, he is drawn into a battle for the survival of her world when the RDA threaten to destroy it.

'Nurse Jackie' star Edie was welcomed to the cast by Cameron, who insisted the actress is ''one of the greats''.

The director tweeted: ''Edie Falco is one of the greats - I can't wait to watch her kick some ass on the big screen.''

The first movie will be released in 2020, followed by the other three in 20121, 2024 and 2025.

The first 'Avatar' film still remains the highest-grossing movie at the worldwide box office, raking in as much as $2.79 billion.